Internal combustion engines that use cylinder deactivation during engine operation have been proposed. Cylinder deactivation shuts down some of the cylinders by stopping opening and closing operation of the intake valves to keep the valves closed for some of the cylinders.
When the internal combustion engine is reactivated from a cylinder deactivation mode to an all cylinder operation mode, torque fluctuation tends to occur due to change in the engine output.
For this reason, for example, the internal combustion engine disclosed in Patent Document 1 reduces the lift amount of the intake valves when the engine is reactivated from the cylinder deactivation mode to reduce the engine output. This configuration restrains the occurrence of torque fluctuation caused by increase in the engine output when the engine is reactivated from the cylinder deactivation mode to the all cylinder operation mode.